Pressure control method and processing device

ABSTRACT

First and second pressure sensors  132  and  134  that perform pressure detection over different pressure detection ranges from each other detect the pressure within a process chamber  102  of an etching device  100 . A pressure controller  144  selects optimal pressure data in correspondence to the pressure inside the process chamber from the pressure data provided by the first and second pressure sensors  132  and  134 . It also analyzes the selected pressure data at a resolution selected in correspondence to the pressure inside the process chamber  102  and thus obtains pressure data achieving a predetermined data density. The pressure controller  134  controls a pressure control valve  130  so as to ensure that the pressure data match preset pressure data.

TECHNICAL FIELD

The present invention relates to a pressure control method and a plasmaprocessing device, and more specifically, it relates to a pressurecontrol method adopted in a means for pressure control provided in asemiconductor manufacturing device.

BACKGROUND ART

A plasma processing device such as a plasma etching device, which iscapable of performing various types of plasma processing, is utilizedduring a semiconductor device manufacturing process in the related art.Such a device processes a workpiece placed within a process chamber bygenerating plasma inside the process chamber with the pressure of itsatmosphere sustained at a level lowered to a preset level. In addition,the pressure inside the process chamber is adjusted by controlling apressure (evacuation quantity) control valve based upon pressure dataprovided by a pressure sensor.

As ultra high integration and super multi-layer structures are becomingincreasingly common in semiconductor devices in recent years, aplurality of films constituted of different materials sometimes must beetched through continuous processing. During such processing, thepressure inside the process chamber may need to be raised/lowered incorrespondence to the material constituting a given film. Some filmmaterials require the processing to be executed at a low pressure ofapproximately several Pa. In addition, a pressure detection range overwhich detection is enabled is set for the pressure sensor and thepressure detection range of a pressure sensor capable of detecting a lowpressure with a high degree of accuracy tends to be smaller under normalcircumstances. For this reason, pressure data to be used in pressurecontrol are sometimes obtained by switching among a plurality ofpressure sensors as appropriate so as to detect the processing pressurelevels at which the individual films are processed and to monitor theoverall change in the pressure occurring inside the process chamber.

However, the processing device in the related art described aboveswitches to a given pressure sensor among the individual pressuresensors based upon switching information that is set in advance. Namely,the pressure controller does not automatically switch among the variouspressure sensors based upon the pressure data provided by the individualpressure sensors. As a result, it is difficult to obtain pressure datathat reflect a drastic pressure change since the selection of theappropriate pressure sensor cannot be made promptly when the pressureinside the process chamber changes greatly. Thus, a problem arises inthat the resulting delay in the control on the pressure inside theprocess chamber tends to cause inconsistency in the processing.

In addition, an increasing need to achieve super-miniaturization ofsemiconductor devices in recent years necessitates super-miniaturizationprocessing to be implemented on a workpiece during an etching process,as well. When the workpiece undergoes the super-miniaturizationprocessing, the pressure inside the process chamber must be rigorouslyadjusted to sustain the level of the pressure inside the process chamberat a predetermined level. Accordingly, accurate pressure control must beachieved through a finer analysis of pressure data provided by apressure sensor. However, if the detected pressure is finely analyzedover a pressure range that does not affect the processing, too, thelength of time required for the arithmetic processing increases. Thismay lead to a problem in that the response of the pressure control valvebecomes poor.

An object of the present invention, which has been completed byaddressing the problems of the related art discussed above, is toprovide a new and improved pressure control method and a new andimproved plasma processing device that provide a solution to problemsidentified above and other problems as well.

DISCLOSURE OF THE INVENTION

In order to achieve the object described above, in a first aspect of thepresent invention, a pressure control method, adopted in a means forpressure control that controls a means for pressure adjustment whichadjusts the pressure inside a process chamber based upon pressure dataprovided by a means for pressure detection which detects the pressureinside the process chamber, with a plurality of means for pressuredetection with different pressure detection ranges from one anotherconnected in the process chamber and at least two of the means forpressure detection having pressure detection ranges overlapping eachother, comprises a step in which the pressure data obtaining ranges overwhich pressure data are to be obtained are each set for one of aplurality of means for pressure detection with different pressuredetection ranges from one another, a step in which pressure dataselection values to be used to select pressure data to be utilized inpressure control from the pressure data provided by the individual meansfor pressure detection are set in correspondence to the individualpressure data obtaining ranges, a step in which the pressure data to beutilized in the pressure control are selected by comparing the pressuredata provided by each means for pressure detection with thecorresponding pressure data selection value and a step in which themeans for pressure adjustment is controlled based upon the selectedpressure data and preset pressure data corresponding to a presetpressure value.

In this method, optimal pressure data provided by the appropriate meansfor pressure detection corresponding to the pressure inside the processchamber can be obtained based upon the pressure data provided by theindividual means for pressure detection. Thus, even though the pluralityof means for pressure detection with varying pressure detection rangesare employed, the required pressure data can be obtained quickly. As aresult, a level of control performance comparable to that achieved byusing a single means for pressure detection is assured even when theplurality of means for pressure detection are employed.

It is desirable that the pressure data obtaining ranges be set so as toallow the pressure detection ranges of the individual means for pressuredetection to overlap each other while ensuring that the pressure dataprovided by the means for pressure detection achieving a higher degreeof pressure detection accuracy are selected from the pressure dataprovided by the plurality of means for pressure detection. In such acase, it becomes possible to obtain the pressure data provided by themeans for pressure detection achieving a high degree of pressuredetection accuracy within a range in which the pressure detection rangesof the individual means for pressure detection overlap each other. Sincethe pressure control can be implemented by using the optimal pressuredata as a result, a further improvement is achieved with regard to thepressure control performance.

It is desirable that the means for pressure adjustment be controlled soas to ensure that the data value indicated by the selected pressure dataconforms to the data value indicated by the preset pressure data. Sincethis achieves control of the means for pressure adjustment whereby thepressure inside the process chamber is set substantially equal to thepreset pressure, the pressure inside the process chamber can besustained at a level equal to the level of the pressure setting.

In addition, in a second aspect of the present invention, a pressurecontrol method adopted in a means for pressure control that controls ameans for pressure adjustment that adjusts the pressure inside a processchamber based upon pressure data provided by a means for pressuredetection that detects the pressure inside the process chamber,comprises a step in which resolution application ranges corresponding toat least two resolutions with which pressure data are analyzed into aplurality of sets of data to virtually change the data density of thepressure data are set in correspondence to a pressure detection range ofthe means for pressure detection, a step in which a resolution selectionvalue to be used to select a single resolution from the resolutions isset based upon the individual resolution application ranges, a step inwhich a single resolution is selected from the resolutions by comparingthe pressure data with the resolution selection value, a step in whichthe data density of the pressure data is virtually changed at theselected resolution and a step in which the means for pressureadjustment is controlled based upon the pressure data having undergonethe data density change and preset pressure data corresponding to apreset pressure value.

In this method, the pressure data obtained from a given means forpressure detection are analyzed at a specific resolution to change thedata density of the pressure data to a predetermined data density. Inaddition, a different resolution can be set in correspondence to aspecific range portion obtained by dividing the pressure detection rangeof the means for pressure detection. As a result, in a specific rangethat contains the preset pressure at which the processing is executed,for instance, accurate pressure information can be obtained by raisingthe resolution to achieve error-free pressure control.

It is desirable that the resolutions be set so as to increase the datadensity of the pressure data within a specific pressure range containingthe preset pressure value. Since accurate pressure information can beobtained over the specific range containing the preset pressure value atwhich the processing is executed in this case, rigorous pressure controlis realized.

In addition, it is desirable that the resolutions be set so as toincrease the data density of the pressure data as the pressure levelshifts from the atmospheric pressure level toward the preset pressurevalue. This allows the pressure detection accuracy to be virtuallyraised as the pressure inside the process chamber shifts from theatmospheric pressure toward the preset pressure value. As a result,rigorous pressure control is achieved during the processing and, at thesame time, the arithmetic operation executed on the pressure data whilethe processing is not in progress can be simplified.

It is desirable that the means for pressure adjustment be controlled sothat the data value indicated by the pressure data having undergone thechange in the data density is made to conform to the data valueindicated by the preset pressure data. By adopting such control, thepressure inside the process chamber can be sustained at the presetpressure level.

In a third aspect of the present invention, a pressure control method,adopted in a means for pressure control that controls a means forpressure adjustment that adjusts the pressure inside a process chamberbased upon pressure data provided by a means for pressure detection thatprotects the pressure inside the process chamber, comprises a step inwhich pressure data obtaining ranges over which the pressure data are tobe obtained are each set for one of a plurality of means for pressuredetection with different pressure detection ranges from one another, astep in which pressure data selection values to be used to selectpressure data to be utilized in pressure control from the pressure dataprovided by the individual means for pressure detection are set incorrespondence to the individual pressure data obtaining ranges, a stepin which resolution application ranges of at least two resolutions withwhich the pressure data are analyzed into a plurality of sets tovirtually change the data density of the pressure data are set for eachof the pressure data obtaining ranges, a step in which a resolutionselection value to be used to select a single resolution from theresolutions corresponding to the selected pressure data is set basedupon the individual resolution application ranges, a step in which thepressure data to be used in pressure control are selected by comparingthe pressure data provided by each individual means for pressuredetection with the corresponding pressure data selection value, a stepin which a single resolution is selected from the resolutions bycomparing the selected pressure data with the resolution selectionvalue, a step in which the data density of the selected pressure data isvirtually changed at the selected resolution and a step in which themeans for pressure adjustment is controlled based upon the pressure datahaving undergone the data density change and preset pressure datacorresponding to a preset pressure value.

In this method, based upon the pressure data, optimal data can beselected and obtained from the pressure data provided by the pluralityof means for pressure detection. As a result, regardless of the numberof means for pressure detection that are provided, control performanceequivalent to the control performance achieved by using the pressuredata from a single means for pressure detection is assured. Furthermore,the method allows a specific resolution to be set in correspondence tothe pressure detection range of each means for pressure detection andalso in correspondence to a specific segment of the range. Consequently,pressure control can be implemented by using the pressure datacorresponding to the required degree of accuracy.

It is desirable that the resolutions be set so as to increase the datadensity of the pressure data within a specific pressure range containingthe preset pressure value.

In addition, it is desirable that the resolutions be set so as toincrease the data density of the pressure data as the pressure levelshifts from the atmospheric pressure toward the preset pressure value.

It is desirable that the means for pressure adjustment be controlled sothat the data value indicated by the pressure data having undergone thechange in the data density is made to conform to the data valueindicated by the preset pressure data.

In addition, the present invention provides a plasma processing devicethat is characterized in that the pressure inside the process chamber iscontrolled by adopting the pressure control method with the outstandingadvantages described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of an etching device in which thepresent invention may be adopted; and

FIG. 2 schematically illustrates the pressure control structure adoptedin the etching device shown in FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

The following is a detailed explanation of a preferred embodimentachieved by adopting the pressure control method according to thepresent invention in a pressure control method implemented inconjunction with a plasma etching device, given in reference to theattached drawings.

(1) Structure of the Etching Device

First, in reference to FIG. 1, the structure of an etching device 100 inwhich the present invention may be adopted is explained. A processchamber 102 is formed inside an electrically conductive airtightprocessing container 104. The processing container 104 is grounded forsafety. In addition, an upper electrode 106 and a lower electrode 108are provided facing opposite each other inside the process chamber 102.The lower electrode 108 is also utilized as a stage on which a workpiecesuch as a semiconductor wafer (hereafter referred to as the “wafer”) Wis placed. A diffusion plate 110 is provided around the lower electrode108. A high frequency power supply 112 is connected to the lowerelectrode 108 via a matcher 114 to apply biasing high frequency powerof, for instance, 13.56 MHz to the lower electrode 108.

In the embodiment, energy conservation is achieved by stopping theoutput from the high frequency power supply 112 while the processsequence is idling. In a standard high frequency power supply (linearamplifier) that is normally utilized, an idling current flows while nosignal is generated to result in a collector loss in a transistor or adrain loss in a FET (field effect transistor). Energy conservation isachieved in the embodiment by turning off the biasing high frequencypower to reduce the loss while the process sequence is idling.

Such energy conservation may be achieved by, for instance, providing arelay for turning on/off the power in an AC power supply line throughwhich the power from a biasing DC source is supplied or by providing acircuit for turning on/off the drive signal for a biasing AC source. Thebiasing source is turned off during the period that elapses followingthe end of a process (after the high frequency power supply 112 isturned off and a predetermined length of time elapses) until the nextunprocessed wafer is transferred into the process chamber 102 or duringthe period that elapses following the end of a process until the nextprocess starts (over a predetermined period before the high frequencypower supply 112 is turned on), for instance.

In addition, a high frequency power supply 116 is connected to the upperelectrode 106 via a matcher 118 to apply plasma-generating highfrequency power of, for instance, 60 MHz to the upper electrode 106.Numerous gas outlet holes 106 a are formed at the upper electrode 106.This structure allows a processing gas provided from a gas supply source120, such as a fluorocarbon gas, to be supplied via a flow-regulatingvalve 122, a switching valve 124 and the gas outlet holes 106 a. The gasinside the process chamber 102 is evacuated by a vacuum pump 126 via thediffusion plate 110, an evacuating passage 128 and a pressure controlvalve (means for pressure adjustment) 130.

A plurality of means for pressure detection with different pressuredetection ranges from one another, e.g., a first pressure sensor 132 anda second pressure sensor 134, are connected in the process chamber 102via switching valves 136 and 138 and pressure detection holes 140 and142 respectively. The first and second pressure sensors 132 and 134 mayeach be constituted of a capacitance manometer. The first pressuresensor 132 detects a pressure within a predetermined pressure range,e.g., 0 Pa˜25 PaV, and outputs a voltage within a range of 0V˜10V aspressure data in correspondence to the detected pressure. The secondpressure sensor 134, on the other hand, detects a pressure within awider pressure range than that of the first pressure sensor 132, e.g., 0Pa˜1000 Pa, and outputs a voltage within a range of 0V˜10V as pressuredata in correspondence to the detected pressure.

A pressure controller 144 is connected to the first and second pressuresensors 132 and 134. The pressure control valve 130 mentioned earlier isconnected to the pressure controller 144. The pressure controller 144controls the pressure control valve 130 based upon the pressure dataprovided by the first and second pressure sensors 132 and 134 and presetpressure data corresponding to a preset pressure value and sets thepressure inside the process chamber 102 to a predetermined pressurelevel. It is to be noted that the pressure control implemented by thepressure controller 144 is to be described in detail later. The pressurecontroller 144 includes various devices to be utilized in the pressurecontrol, such as an A/D (analog-digital) converter (not shown) whichconverts the voltages output by the first and second pressure sensors132 and 134 as analog data to digital data.

(2) Pressure Control Method

Next, a setting process (a) and a control process (b) implemented in thepressure control method to control the pressure inside the processchamber 102, which constitutes the core of the present invention, areindividually explained.

(a) Setting Process

During the setting process (a), pressure data obtaining ranges, pressuredata selection values, resolutions, resolution application ranges,resolution selection values and a control pressure value are set at thepressure controller 144.

(a-1) Setting Pressure Data Obtaining Ranges and Pressure Data SelectionValues

The pressure data obtaining, ranges are set to determine whether thepressure data provided by the first pressure sensor 132 or the pressuredata provided by the second pressure sensor 134 are to be used inpressure control. In addition, the pressure data selection values arevalues (threshold values) set in correspondence to the individualpressure data obtaining ranges to be used to select the pressure dataprovided by either the first pressure sensor 132 or the second pressuresensor 134.

As explained earlier, the first pressure sensor 132 is capable ofdetecting a pressure within the 0 Pa˜25 Pa range. The second pressuresensor 134 is capable of detecting a pressure within the 0 Pa˜1000 Parange. In addition, the first pressure sensor 132 achieves a higherdegree of pressure detection accuracy compared to the second pressuresensor 134. For this reason, it is desirable to utilize the pressuredata provided by the first pressure sensor 132 over the pressure rangein which a pressure can be detected with the first pressure sensor 132.Thus, the pressure data obtaining range is set to 0 Pa˜25 Pa for thefirst pressure sensor 132. The pressure data obtaining range is set to25 Pa˜1000 Pa for the second pressure sensor 134.

The pressure data selection values should be set to voltage valuescorresponding to 25 Pa so as to obtain specific pressure data from theindividual pressure data obtaining ranges set for the first and secondpressure sensors 132 and 134. Namely, the pressure data selection valuefor the first pressure sensor 132 should be set to 10V. Incorrespondence to the pressure level 25 Pa, whereas the pressure dataselection value for the second pressure sensor 134 should be set to0.25V in conformance to the pressure level 25 Pa. Thus, when thepressure data corresponding to the voltage value 0.25V are input fromthe second pressure sensor 134 as the pressure is lowered, the pressurecontroller 144 switches to the control implemented based upon thepressure data from the first pressure sensor 132. If, on the other hand,the pressure data corresponding to the pressure value 10V are input fromthe first pressure sensor 132 as the pressure is raised, the pressurecontroller 144 switches to the control implemented based upon thepressure data from the second pressure sensor 132*[1]. As a result, itis possible to select optimal pressure data from the pressure dataprovided by the first and second pressure sensors 132 and 134, incorrespondence to the pressure level in the process chamber 102. Thus,it is possible to assure a level of control performance which iscomparable to that achieved in pressure control implemented based uponpressure data obtained from a single pressure sensor.

(a-2) Setting Resolutions, Resolution Application Ranges and ResolutionSelection Values

The resolutions need to be set to virtually change the pressuredetection accuracy of the first pressure sensor 132 or the secondpressure sensor 134 by analyzing the pressure data provided by the firstpressure sensor 132 or the second pressure sensor 134 and thus changingthe data density of the pressure data. In addition, the resolutionapplication ranges are set to determine which of the resolutions shouldthe used within each of the varying pressure data obtaining ranges setfor the first and second pressure sensors 132 and 134. The resolutionselection values are values (threshold values) each set to be used toselect the resolution to be adopted based upon the resolutionapplication ranges.

In the embodiment, gate electrodes are formed by etching a polysiliconfilm formed on an oxide film (an SiO2 film) and a tungsten silicide filmformed on the polysilicon film through continuous processing which is tobe detailed later. It is desirable to process the tungsten silicide filmat a low pressure of, for instance, 0.4 Pa. In addition, the polysiliconfilm should be processed at a pressure higher than that at which thetungsten silicide film is processed, e.g., 15 Pa. For this reason,accurate pressure control must be achieved with regard to the varyingprocessing pressure levels. Furthermore, particularly rigorous pressurecontrol must be achieved during the processing of the tungsten silicidefilm which is implemented at low pressure.

First, two varying levels of resolution, for instance, should be set toanalyze the pressure data from the first pressure sensor 132. Namely, aresolution which allows pressure data to be obtained with the highestdegree of accuracy, e.g., accuracy in units of 0.01 Pa, should be set incorrespondence to the 0 Pa˜10 Pa pressure range which contains theprocessing pressure level to be set for processing the tungsten silicidefilm. In addition, a resolution which allows pressure data to beobtained with an accuracy in units of, for instance, 0.025 Pa should beset in correspondence to the 10 Pa˜25 Pa pressure range containing theprocessing pressure level to be set to process the polysilicon film.Accordingly, the resolution application ranges of the first pressuresensor 132 are 0 Pa˜10 Pa and 10 Pa˜25 Pa.

A voltage equal to or lower than 4V is output from the first pressuresensor 132 in the 0 Pa˜10 Pa range. Accordingly, the voltage 4Vcorresponding to 10 Pa output by the first pressure sensor 132, shouldbe divided by, for instance, 1000. By obtaining pressure datarepresented by a voltage indicated in units of 4 mV through thisresolution setting, it is possible to implement pressure control inunits of 0.01 Pa. A voltage within a range of 4 V˜10V is output from thefirst pressure sensor 132 in the 10 Pa˜25 Pa pressure range.Accordingly, the 10V corresponding to 25 Pa output by the first pressuresensor 132 should be divided by, for instance, 1000. By obtainingpressure data constituted of a voltage indicated in units of 10 mVthrough this resolution setting, it is possible to implement pressurecontrol in units of 0.025 Pa.

The voltage value 4V corresponding to 25 Pa is set as the resolutionselection value for the pressure data from the first pressure sensor 132so as to allow either of the resolutions to be used in correspondence tothe resolution application range. This setting allows the pressurecontroller 114 to select the appropriate resolution by using the outputvoltage 4V from the first pressure sensor 132 as the cutoff point.

Two varying levels of resolution, for instance, should be set to analyzethe pressure data from the second pressure sensor 134, as in the firstpressure sensor 132. Namely, a resolution which allows pressure data tobe obtained with accuracy in units of 0.01 Pa, for instance, should beset in correspondence to the 25 Pa˜100 Pa pressure range. In addition, aresolution which allows pressure data to be obtained with accuracy inunits of, for instance, 1 Pa should be set in correspondence to the 100Pa˜1000 Pa pressure range. Accordingly, the resolution applicationranges of the second pressure sensor 134 are 25 Pa˜100 Pa and 100Pa˜1000 Pa.

A voltage equal to or lower than 1V is output from the second pressuresensor 134 in the 25 Pa˜100 Pa range. Accordingly, the voltage 1Vcorresponding to 100 Pa output by the second pressure sensor 134, shouldbe divided by, for instance, 1000. By obtaining pressure datarepresented by a voltage indicated in units of 1 mV through thisresolution setting, it is possible to implement pressure control inunits of 0.1 Pa. A voltage within a range of 1V˜10V is output from thesecond pressure sensor 134 in the 100 Pa˜1000 Pa range. Accordingly, the10V corresponding to 1000 Pa output by the second pressure sensor 134,should be divided by, for instance, 1000. By obtaining pressure datarepresented by a voltage indicated in units of 10 mV through thisresolution setting, it is possible to implement pressure control inunits of 1 Pa.

The voltage value 1V corresponding to 100 Pa is set for the resolutionselection value for the pressure data from the second pressure sensor134 so as to allow either of the resolutions to be used incorrespondence to resolution application range. This setting allows thepressure controller 114 to select the appropriate resolution by usingthe output voltage 1V from the second pressure sensor 134 as the cutoffpoint. As a result, it becomes possible to increase the accuracy of thepressure data as the pressure level nears the processing pressure level.Thus, more rigorous pressure control is enabled during the processing,whereas fast pressure control is achieved while the processing is not inprogress.

(a-3) Setting a control pressure value

The control pressure value is used in the pressure control and iscalculated based upon a pressure value set in units of Pa at thepressure controller 144. As explained earlier, the pressure controller144 is capable of obtaining pressure data in units of as fine as 0.01Pa. In addition, the pressure can be detected over a range of up to 0Pa˜1000 Pa. Accordingly, the control pressure value is set incorrespondence to units of 0.01 Pa by dividing 1000 Pa by 100,000. Thus,the pressure controller 144 is enabled to implement pressure controlwhen, for instance, a predetermined pressure value of 0.3 Pa is input,based upon a control pressure value which is calculated to be 30 incorrespondence to 0.3 Pa. By adopting this method, the pressure can beset with ease in units of 0.01 Pa over the pressure detection ranges ofboth the first and second pressure sensors 132 and 134.

(b) Control Process

Next, in reference to FIGS. 1 and 2, the procedure of the pressurecontrol implemented during the etching process is explained. First,prior to the etching process, the first and second pressure sensors 132and 134 undergo an offset adjustment (0 adjustment). In addition, apressure value of 0.4 Pa at which the polysilicon film is to beprocessed and a pressure value of 15 Pa at which the tungsten silicidefilm is to be processed are set at the pressure controller 144. Thepressure controller 144 converts the preset pressure values to controlpressure values as described above and uses the control pressure valuesresulting from the conversion in the control. After various othersettings are made, the wafer W mentioned earlier is placed on the lowerelectrode 108. Next, the processing gas provided from the gas supplysource is supplied into the process chamber 102. At the same time, thegas inside the process chamber 102 is evacuated with the vacuum pumpP126. Through this evacuation, the pressure inside the process chamber102 is lowered as shown in FIG. 2.

If the pressure inside the process chamber 102 is within a range of 100Pa˜1000 Pa, a voltage 10 V is input from the first pressure sensor 132to the pressure controller 144 and also a voltage within a range of 1V˜10 V corresponding to the actual pressure level is input from thesecond pressure sensor 134 to the pressure controller 144. The pressurecontroller 144 judges that the value of the voltage input from thesecond pressure sensor 134 is larger than the pressure data selectionvalue 0.25 V corresponding to 25 Pa and thus selects of the pressuredata provided by the second pressure sensor 134. In addition, thepressure controller 144 judges that the value of the voltage input fromthe second pressure sensor 134 is larger than the resolution selectionvalue 1V corresponding to 100 Pa and accordingly analyzes the pressuredata from the second pressure sensor 134 with the resolution thatprovides a pressure value indicated in units of 1 Pa. Thus, the pressurecontroller 144 is enabled to control the pressure control valve 130based upon the pressure data provided in units of 1 Pa.

If the pressure inside the process chamber 102 is lowered to a level inthe 25 Pa˜100 Pa range, a voltage within a range of 0.25 V˜1V is inputfrom the second pressure sensor 134 to the pressure controller 144. Thepressure controller 144 judges that the value of the voltage input fromthe second pressure sensor 134 is equal to or smaller than theresolution selection value 1V and accordingly switches the resolution soas to control the pressure control valve 130 based upon the pressuredata provided in units of 0.1 Pa.

If the pressure inside the process chamber 102 is further reduced to alevel lower than 25 Pa, a voltage lower than 10 V and a voltage lowerthan 0.25 V are input respectively from the first pressure sensor 132and the second pressure sensor 134 to the pressure controller 144. Thepressure controller 144 judges that the value of the voltage input fromthe second pressure sensor 134 is smaller than the pressure dataselection value 0.25 V and thus selects the pressure data provided bythe first pressure sensor 132. In addition, the pressure controller 144judges that the value of the voltage input from the first pressuresensor 132 is larger than the resolution selection value 4 Vcorresponding to 10 Pa and accordingly analyzes the pressure data fromthe first pressure sensor 132 with the resolution which provides apressure value in units of 0.025 Pa.

As the pressure inside the process chamber 102 reaches 15 Pa, the levelset for etching the tungsten silicide film, the pressure controller 144controls the pressure control valve 130 so as to sustain this pressurelevel. When the pressure is stabilized at the 15 Pa level, the highfrequency power of 60 MHz mentioned earlier is applied to the upperelectrode 106 to convert the processing gas to plasma. In addition, thehigh frequency power of 13.56 MHz mentioned earlier is applied to thelower electrode 108 to induce plasma to the wafer W. Thus, the tungstensilicide film is etched and gate electrodes are formed.

Once the specific etching process is implemented on the tungstensilicide film, the polysilicon film is etched. Immediately before thepolysilicon film becomes exposed, the pressure controller 144 lowers thepressure inside the process chamber 102 to the 0.4 Pa level at which thepolysilicon film is to be processed by controlling the pressure controlvalve 130. When the pressure inside the process chamber 102 becomesequal to or lower than 10 Pa, a voltage equal to or lower than 4 V isinput from the first pressure sensor 132 to the pressure controller 144.The pressure controller 144 judges that the value of the voltage inputfrom the first pressure sensor 132 is equal to or lower than theresolution selection value 4 V and accordingly switches the resolutionto control the pressure control valve 130 based upon the pressure dataprovided in units of 0.01 Pa. In addition, as the pressure inside theprocess chamber 102 reaches the 0.4 Pa level, the pressure controller144 implements control on the pressure control valve 130 so as tosustain this pressure level. Through this pressure control, gateelectrodes achieving a specific shape are formed at the polysilicon filmas well. It is to be noted that the frequencies of the high frequencypower applied to the upper electrode 106 and the lower electrode 108 andthe type of processing gas supplied into the process chamber 102 whileetching the polysilicon film may be varied as necessary.

While the invention has been particularly shown and described withrespect to the embodiment thereof by referring to the attached drawings,the present invention is not limited to this example and it will beunderstood by those skilled in the art that various changes in form anddetail may be made therein without departing from the spirit, scope andteaching of the invention.

For instance, while an explanation is given in reference to theembodiment on an example in which the pressure inside the processchamber is detected by using two pressure sensors, the present inventionis not limited to this example. The present invention may also beadopted in control achieved by detecting the pressure with a singlemeans for pressure detection or with three or more means for pressuredetection as well.

In addition, while the present invention is explained in reference tothe embodiment in which the pressure data from the first and secondpressure sensors are analyzed with two different resolutions, thepresent invention is not limited by this example. The present inventionmay instead be adopted in control achieved by analyzing pressure datafrom a pressure sensor with three or more different resolutions incorrespondence to the varying pressure settings.

While an explanation is given in reference to the embodiment on anexample in which the pressure inside the process chamber of aplane-parallel plasma etching device is controlled, the presentinvention is not limited to this example. The present invention may alsobe adopted in pressure control implemented to control the pressureinside the process chamber of any of various types of plasma processingdevice including inductively coupled plasma processing devices andmicrowave plasma processing devices.

According to the present invention, even when the pressure inside theprocess chamber is detected by employing a plurality of means forpressure detection, appropriate pressure data can be quickly selectedfrom the pressure data provided by the individual means for pressuredetection to be used in the pressure control. Thus, a high degree ofcontrol performance comparable to that achieved in control implementedbased upon pressure data from a single means for pressure detection isassured even though the pressure is detected by the plurality of meansfor pressure detection. In addition, the pressure detection accuracy ofthe means for pressure detection can be improved virtually. As a result,the pressure inside the process chamber can be controlled with a highdegree of accuracy. Furthermore, according to the present invention, thepressure data used the pressure control can be obtained through softwareprocessing. Consequently, even when the pressure inside the processchamber changes drastically, the pressure inside the process chamber canbe detected almost concurrently as the pressure change occurs. Thus,pressure control which is implemented in conformance to any pressurechange is achieved.

INDUSTRIAL APPLICABILITY

The present invention may be adopted when implementing processing thatrequires pressure control in a semiconductor device manufacturingprocess and in particular, it may be adopted in super-miniaturizationprocessing implemented on a workpiece during which the pressure insidethe process chamber needs to be sustained at a predetermined levelthrough rigorous control.

1. A pressure control method for use in a controlling pressure inside aprocess chamber based on pressure data obtained by a plurality ofpressure sensors, the pressure sensors each connected to the processchamber and being configured to detect the pressure inside the processchamber, the method comprising: setting a pressure detection range foreach of the pressure sensors, the pressure detection range for each ofthe pressure sensors being different from one another, at least two ofthe pressure detection ranges overlapping with each other; setting aselection value for each of the pressure sensors, wherein the selectionvalue is used for selecting the pressure sensor to be used to obtain thepressure data for use in controlling the pressure inside the processchamber; selecting the pressure data to be used in controlling thepressure inside the process chamber by comparing the pressure dataobtained by each of the pressure sensors to the corresponding selectionvalue in each of the pressure sensors; and adjusting the pressure insidethe process chamber based on the selected pressure data and presetpressure data.
 2. A pressure control method according to claim 1,wherein the step of selecting the pressure data comprises selecting thepressure data obtained by one of the pressure sensors, the selectedpressure data having a higher degree of detection accuracy than otherpressure data obtained by the other pressure sensors.
 3. A pressurecontrol method according to claim 1, wherein the step of adjusting thepressure inside the process chamber comprises controlling a pressurecontroller to match the pressure inside the process chamber to a presetpressure by comparing the selected pressure data with the presetpressure data.
 4. A pressure control method according to claim 3,wherein the step of controlling the pressure controller comprisesadjusting a pressure control valve to match the pressure inside theprocess chamber to the preset pressure.
 5. A pressure control methodaccording to claim 3, wherein the process chamber is used to manufacturesemiconductor device.
 6. A pressure control method for use in acontrolling pressure inside a process chamber based on pressure dataobtained by a plurality of pressure sensors, the pressure sensors beingconfigured to detect the pressure inside the process chamber andgenerate pressure data, the method comprising: setting at least tworesolutions for each of the pressure sensors having a pressure detectionrange, each of the resolutions having a resolution application rangesetting a resolution selection value to be used to select a singleresolution from the at least two resolutions based on the individualresolution application ranges; selecting the single resolution from theat least two resolutions by comparing the pressure data with theresolution selection value; virtually changing the data density of thepressure data at the selected resolution; and adjusting the pressureinside the process chamber based on the pressure data having the datadensity changed at the selected resolution and preset pressure datacorresponding to a preset pressure.
 7. A pressure control methodaccording to claim 6, wherein the resolutions are set so as to increasethe data density of the pressure data within a specific pressure rangecontaining the preset pressure.
 8. A pressure control method accordingto claim 6, wherein the resolutions are set so as to increase the datadensity of the pressure data as the pressure inside the process chambershifts from an atmospheric pressure toward the preset pressure.
 9. Apressure control method according to claim 6, wherein the step ofadjusting the pressure inside the process chamber comprises controllinga pressure controller to match the pressure data having the data densitychanged at the selected resolution with the preset pressure data.
 10. Apressure control method for use in controlling pressure inside a processchamber based on pressure data obtained by a plurality of pressuresensors, the pressure sensors being configured to detect the pressureinside the process chamber and generate pressure data, the methodcomprising: setting a pressure detection range to each of the pressuresensors, the pressure detection ranges of the pressure sensors beingdifferent from one another, at least two of the pressure detectionranges being overlapping with each other; setting a selection value toeach of the pressure sensors, wherein the selection value is used forselecting the pressure sensor to be used to obtain the pressure data foruse in controlling the pressure inside the process chamber; setting atleast two resolutions for each pressure detection range of the pressuresensors, each of the resolutions having a resolution application rangesetting a resolution selection value to be used to select a singleresolution from the at least two resolutions based on the individualresolution application ranges; selecting the pressure data to be used incontrolling the pressure inside the process chamber by comparing thepressure data obtained by each of the pressure sensors to thecorresponding selection value in each of the pressure sensors; andselecting the single resolution from the at least two resolutions bycomparing the pressure data with the resolution selection value;virtually changing the data density of the pressure data at the selectedresolution; and adjusting the pressure inside the process chamber basedon the pressure data having the data density changed at the selectedresolution and preset pressure data corresponding to a preset pressure.11. A pressure control method according to claim 10, wherein the step ofselecting the pressure data comprises selecting the pressure dataobtained by one of the pressure sensors, the selected pressure datahaving a higher degree of detection accuracy than other pressure dataobtained by the other pressure sensors.
 12. A pressure control methodaccording to claim 10, wherein the resolutions are set so as to increasethe data density of the pressure data within a specific pressure rangecontaining the preset pressure.
 13. A pressure control method accordingto claim 10, wherein the resolutions are set so as to increase the datadensity of the pressure data as the pressure inside the process chambershifts from an atmospheric pressure toward the preset pressure.
 14. Apressure control method according to claim 10, wherein the step ofadjusting the pressure inside the process chamber comprises controllinga pressure controller to match the pressure data having the data densitychanged at the selected resolution with the preset pressure data.
 15. Aplasma processing device for implementing a plasma processing on aworkpiece placed inside a process chamber, comprising: means fordetecting pressure inside said process chamber, the means for detectingthe pressure comprising a plurality of pressure sensors each having adifferent pressure detection range from one another and connected tosaid process chamber, each of the sensors configured to generatepressure data, at least two of said pressure sensors having pressuredetection ranges overlapping each other; means for setting a selectionvalue for each of the pressure sensors, the selection value used forselecting which of the pressure data is to be utilized to control thepressure inside the process chamber; means for selecting the pressuredata to be utilized in said pressure control by comparing the pressuredata provided by each of the plurality of pressure sensors with thecorresponding selection values; and means for adjusting the pressureinside the process chamber based upon said selected pressure data andpreset pressure data corresponding to a preset pressure value.
 16. Aplasma processing device comprising: means for detecting pressure insidea process chamber, the means for detecting the pressure comprising aplurality of pressure sensors each having a different pressure detectionrange from one another; means for adjusting the pressure inside theprocess chamber based on pressure data detected by the means fordetecting the pressure; means for setting at least two differentresolutions for each of the pressure sensors; means for setting aresolution application range for each of the pressure sensors incorrespondence to the pressure detection range of the correspondingpressure sensor; means for setting a resolution selection value used forselecting one resolution from the at least two resolutions; means forselecting the one resolution from the at least two resolutions bycomparing the pressure data with the resolution selection value; meansfor virtually changing the data density of the pressure data at theselected resolution; and means for controlling the means for adjustingthe pressure inside the process chamber based upon the pressure datahaving the data density changed and preset pressure data correspondingto a preset pressure value.